Horizontal Spin Recovery - with Magnus Effect?

[BABAR]

I don't believe even the Alway bros. touched on possible lift generation from either the fins or the horizontal position of the BSR. http://web.archive.org/web/20071015035108/http://members.aol.com/petealway/srrg.htm
Interestingly they did note that a SPINNING BSR tends to be more significantly successful at backsliding. "We found that models that spin on recovery can fall sideways or glide over a larger part of the predicted range BCP-CG-CLA relationships".

Thanks. I am beginning to think that BSR and HSR are, to borrow from Toy Story 1, “falling with style.” Meaning the main descent slowing mechanism is increased drag due to horizontal orientation. Not knocking it, it still works.

 

[ksaves2]

Just stumbled into this thread. Very interesting. Only thing I can add is I think I still have a conventional dual deploy long necked rocket that upon deployment of the drogue would lie completely horizontal and make a wide roughly ~100 foot diameter spiral descent dragging the drogue. Darndest thing I ever saw. Wished I had a video camera to record but it was a long time ago. Main would deploy and it came down in the usual fashion
I remember it did it a couple of times and wasn't consistent. Sometimes drogue would deploy and the rocket would descend in the usual fashion. Kurt

 

[Rktman]

Thanks. I am beginning to think that BSR and HSR are, to borrow from Toy Story 1, “falling with style.” Meaning the main descent slowing mechanism is increased drag due to horizontal orientation. Not knocking it, it still works.

S'long as it comes down more horizontally than vertically, I'm happy.

 

[jhill9693]

Just stumbled into this thread. Very interesting. Only thing I can add is I think I still have a conventional dual deploy long necked rocket that upon deployment of the drogue would lie completely horizontal and make a wide roughly ~100 foot diameter spiral descent dragging the drogue. Darndest thing I ever saw. Wished I had a video camera to record but it was a long time ago. Main would deploy and it came down in the usual fashion
I remember it did it a couple of times and wasn't consistent. Sometimes drogue would deploy and the rocket would descend in the usual fashion. Kurt

I too have experienced this with my Estes Star Orbiter and a JLCR that failed. Spun horizontally the whole way down and was recovered without damage in sand.

 

[ksaves2]

I too have experienced this with my Estes Star Orbiter and a JLCR that failed. Spun horizontally the whole way down and was recovered without damage in sand.

Yeah,

Wished all my rockets would come down that way as I think it would help decrease the recovery walk as the rocket spirals, it flies upwind for a time. We're talking gentle 100 to 200 foot spiral/circles. With the rocket under drogue chute flying upwind in a portion of the spiral, it has the potential of decrease the drift.
I have no idea of why this phenomena occurs and will shut my mouth up now as I'm off-topic on this thread. (Sorry) Kurt

 

[Dotini]

The latest experiments at 60 Acres this morning were cut short due to a variety of problems, and nothing conclusive was learned about the relative descent times of the Backslider and HSR systems. We'll keep trying.

One side experiment that did prove entirely productive was the use of a 2nd ejection event port at the base of the main tube, and on the opposite side of the tube as the upper port. A stronger pinwheeling effect is the intention



Hole is punched separately through both tube and coupler, then aligned upon gluing of the coupler. The purpose is more reliable insertion into HSR and elimination of ballistic outcomes. Of course above all, the correct motor and delay must be used.

 

[BABAR]

Yeah,

Wished all my rockets would come down that way as I think it would help decrease the recovery walk as the rocket spirals, it flies upwind for a time. We're talking gentle 100 to 200 foot spiral/circles. With the rocket under drogue chute flying upwind in a portion of the spiral, it has the potential of decrease the drift.
I have no idea of why this phenomena occurs and will shut my mouth up now as I'm off-topic on this thread. (Sorry) Kurt

Actually, I don’t think this is a rare phenomenon. I have several streamer rockets where it seems like the streamer is just sufficient to balance the nose cone (so the streamer doesn’t pull the rocket nose up, nor the nose cone pull the rocket nose down. Sounds like would have to be carefully balanced, but maybe due to the asymmetric fins on my many of my streamer rockets, most if not all of them seem to come down horizontally, and there does seem to be some “backward”” velocity.

 

[BABAR]

The latest experiments at 60 Acres this morning were cut short due to a variety of problems, and nothing conclusive was learned about the relative descent times of the Backslider and HSR systems. We'll keep trying.

One side experiment that did prove entirely productive was the use of a 2nd ejection event port at the base of the main tube, and on the opposite side of the tube as the upper port. A stronger pinwheeling effect is the intention

View attachment 533723
View attachment 533724
Hole is punched separately through both tube and coupler, then aligned upon gluing of the coupler. The purpose is more reliable insertion into HSR and elimination of ballistic outcomes. Of course above all, the correct motor and delay must be used.

Couple of pluses to the mod, no real minuses

1. May provide a stronger torque displacement, although I think the forward hole is likely “enough”

2. Rotating the “heavy” end of rocket (expended motor and fins) in opposite direction as the nose may produce LESS stress on the body tube than just rotating the nose end, as the ”lever” point will be close to mid body between the two holes, as opposed single forward hole which likely stresses the CG closer to motor mount (longer lever arm.) Maybe @prfesser or @ksaves2 can chime in whether this is correct or not.

I haven’t built nearly the number you have, and yours are for the most Part longer than mine, have you experience bent body tubes you feel were caused by excessive torque force?

no minuses, still one “neutral”: the final orientation of the rocket once the torque force wears off (pretty quickly I imagine) is still I believe completely random, and I think here is still always the small chance (just like the green pocket of a roulette wheel) the rocket completes its torque motion nose near straight down. I am not convinced there is any way to completely avoid this, although again the LONGER the rocket the SMALLER the straight down pocket. I think the “pocket” is intrinsically SMALLER (less likely to fail and recover ballistically) for HSR than Back Slide Redovery, as if there is just a small offset from vertical it will be enough to start rotation. Once started, rotation is a positive “vicious cycle” as once rocket begins to turn it TENDS to ”force” the rocket even MORE horizontal, which makes it catch more air and spin faster……

 

[Dotini]

One of my most successful models is the venerable Magnus X-1. It's survived dozens of flights and numerous accidents, yet still performs with exceptionally reliable HSR tight spirals, and landings on all sorts of surfaces have never damaged a fin. The fins are exceptionally labor intensive. The inner panel is 1/16" balsa, papered, with a full periphery of hardwood dowelling.


X-1 on left has crumpled tube "repaired" with tape and dowels, but still performs exceptionally. New model on right is an attempt to recapitulate the X-1 in a larger size and with much less labor. The fins are styrene angles of 0.050" thickness.

 

[BABAR]

One of my most successful models is the venerable Magnus X-1. It's survived dozens of flights and numerous accidents, yet still performs with exceptionally reliable HSR tight spirals, and landings on all sorts of surfaces have never damaged a fin. The fins are exceptionally labor intensive. The inner panel is 1/16" balsa, papered, with a full periphery of hardwood dowelling.

View attachment 533941

X-1 on left has crumpled tube "repaired" with tape and dowels, but still performs exceptionally. New model on right is an attempt to recapitulate the X-1 in a larger size and with much less labor. The fins are styrene angles of 0.050" thickness.

Of course, enemy of “good” is “better”

I am wondering if your design might benefit from 2 styrene bands, maybe 1/4 inch long, around the front and back of the fins. The 1/2 box fin design is perfect for boost stability and initiation of spin. The down side is the lateral 90 degree joint during descent is on the forward edge relative to spin, and is going to strike really hard on landing. Given the angle, it is gonna “catch” the ground and result in an abrupt near instantaneous cessation of spin. Which means you are bleeding off a LOT of kinetic rotational energy very quickly, hence a lot of stress.

The RINGS may allow the rocket after it hits to keep spinning for a short time, obviously it will still come to a stop but it maaaaay slow the dissipation of energy so less abrupt stress. Cost is time building (never negligible), drag and weight. Although it will add a bit of additional stability.

Also thinking SPAN is a factor, larger hemispans spin better but also have longer moment arm and therefore more stress.

I really think your tube fins are the bee’s knees. They look tough, they bounce, and the curve is in the right direction to slowly dissipate the energy.

@jhill9693 ’s design is ingenious as well. I really wonder whether you could make the fin span a bit longer, cut slots in the 50% of the chord so the slide into each other (a bit like FlisKits DooDad), you might have the perfect Cub Scout rapid build rocket.

 

[Dotini]

Of course, enemy of “good” is “better”

I am wondering if your design might benefit from 2 styrene bands, maybe 1/4 inch long, around the front and back of the fins. The 1/2 box fin design is perfect for boost stability and initiation of spin. The down side is the lateral 90 degree joint during descent is on the forward edge relative to spin, and is going to strike really hard on landing. Given the angle, it is gonna “catch” the ground and result in an abrupt near instantaneous cessation of spin. Which means you are bleeding off a LOT of kinetic rotational energy very quickly, hence a lot of stress.

The RINGS may allow the rocket after it hits to keep spinning for a short time, obviously it will still come to a stop but it maaaaay slow the dissipation of energy so less abrupt stress. Cost is time building (never negligible), drag and weight. Although it will add a bit of additional stability.

Also thinking SPAN is a factor, larger hemispans spin better but also have longer moment arm and therefore more stress.

I really think your tube fins are the bee’s knees. They look tough, they bounce, and the curve is in the right direction to slowly dissipate the energy.

@jhill9693 ’s design is ingenious as well. I really wonder whether you could make the fin span a bit longer, cut slots in the 50% of the chord so the slide into each other (a bit like FlisKits DooDad), you might have the perfect Cub Scout rapid build rocket.

All good material for thought and experiment, especially the narrow ring idea.

Let me bring up another thing I think I am slowly learning the hard way; embrittlement and premature breakage of plastic fins due to paint application. I'm not a chemist, so I cannot prove this academically. But I've built and flown so very many models with plastic fins that my Neanderthal brain stem is wakening to the fact that the bigger and heavier I make my models, the more rapidly painted flexible PETG plastic fins will break off just above the fillet. I have to add that I had a number of failures where the entire fin assembly, fillets included, simply departs company due to failure of the CA joint between the fin and the tube. This includes models in which there is a broad-base styrene angle or tee-section spreading the load between fin and tube. I've also had one Gorilla glue joint fail in such a fashion where everything goes, including the fillets. I hasten to add that I always try to prep the tube and the parts with cleaning and light abrasion before joining. All this hard won experience is forcing me to revisit previous designs such as X-1. IMHO, at the end of the day, there is a lot to be said for cleverly built models of balsa and wood glue, the lighter the better.

Allow me to conclude by reprinting the very first image of this thread:

To build such a design in balsa, whether by gluing two pieces together in a sufficiently strong joint, or by successfully softening and bending the grain, may be good solutions for a very light model.

“We shall not cease from exploration, and the end of all our exploring will be to arrive where we started and know the place for the first time.”
- T.S. Elliot

 

[lakeroadster]

All good material for thought and experiment, especially the narrow ring idea.

Let me bring up another thing I think I am slowly learning the hard way; embrittlement and premature breakage of plastic fins due to paint application. I'm not a chemist, so I cannot prove this academically. But I've built and flown so very many models with plastic fins that my Neanderthal brain stem is wakening to the fact that the bigger and heavier I make my models, the more rapidly painted flexible PETG plastic fins will break off just above the fillet. I have to add that I had a number of failures where the entire fin assembly, fillets included, simply departs company due to failure of the CA joint between the fin and the tube. This includes models in which there is a broad-base styrene angle or tee-section spreading the load between fin and tube. I've also had one Gorilla glue joint fail in such a fashion where everything goes, including the fillets. I hasten to add that I always try to prep the tube and the parts with cleaning and light abrasion before joining. All this hard won experience is forcing me to revisit previous designs such as X-1. IMHO, at the end of the day, there is a lot to be said for cleverly built models of balsa and wood glue, the lighter the better.

Allow me to conclude by reprinting the very first image of this thread:

To build such a design in balsa, whether by gluing two pieces together in a sufficiently strong joint, or by successfully softening and bending the grain, may be good solutions for a very light model.

“We shall not cease from exploration, and the end of all our exploring will be to arrive where we started and know the place for the first time.”
- T.S. Elliot

This thread is a plethora of great ideas....

For balsa or basswood fins that are curved, it would seem not that difficult to make these out of 1/32 material, 2 or 3 ply's that are glued together and then clamped into a form? That would result in a strong lightweight fin. Perhaps build the form from some PVC pipe, cut in half longitudinally? Easy Peazy. I might take a look at this out in the barn today.

For strong fin attachment, on minimal diameter rockets, try this... tip of the hat to @AeroTech for this technique.

​

Or perhaps give @jhill9693 Keep It Simple Slick 3 fin design a try that self supports the fins

​

 

[lakeroadster]

Here's some photos of my adventure in making a curved fin fixture / form this morning.

I used a 5-ply construction of (3) pieces of 11 mil printer paper and (2) pieces of 1/16 balsa. But the form could be used for whatever witches' brew of materials you prefer. I used Gorilla wood glue, with a little water added.

I'll report back after the plywood / paper composite has had 24 hours to drive.

 

[BABAR]

Since we are already outside the box, entertaining even crazier ideas doesn’t seem unreasonable (we already have two “unbaked” design threads which are highly popular!)

my first is frangible recovery

https://www.rocketryforum.com/threads/frangible-assisted-recovery.165724/#post-2125851
put soda straws or popsicle sticks or ROUNDED toothpicks taped or otherwise loosely attached (firm enough to hang on for boost, though) sticking outward. They will INCREASE stability marginally, they will probably add a good bit of drag but as @Daddyisabar says, “trust in thrust”, you aren’t going for altitude records. These are literally designed to bend or break on impact. For those poopooing the idea, remember that Apollo spacecraft and the Mars landers all had ablative heat shields designed literally to burn up

second Idea is sort of a modification of the first, fin attachments which are firm in boost orientation, but easily “pop off” (and hopefully can be easily put back in place) on impact. Vector or impact force is orthogonal to launch/boost stress, so shallow “pockets” might fill the bill. Also the use of polystyrene fins which are both stronger and more flexible (unfortunately likely heavier) than balsa is a plus.

I think your tubes are thinner than mine and more flexible. Not sure of their weight compared to regular cardboard body tubes. An option may be to use the standard 6 tube fins around an identical size central body tube, using one of your tubes AS the rocket body tube, either with a piece of parchment paper rolled up inside or a stuffer tube or something, so you don't melt the plastic. For the tube fins, easy enough to glue them in pairs (they align perfectly, just setting them a flat surface), then attaching each of the three pairs to the body tube (where they will also self-align.) Then cut out segments, sort of like the

https://www.rocketryforum.com/threa...horizontal-spin-recovery.173916/#post-2304344
Mine hasn't flown yet, still waiting to find a field or else go see @Ronz Rocketz and @kuririn in Hawaii (or I should just mail it to you!)

Advantage may be that with 6 tubes, you can use a relatively shorter span, the tubes even with the cutouts are mutually supporting so stronger, and it's a pretty easy build.

 

[Ronz Rocketz]

Mine hasn't flown yet, still waiting to find a field or else go see @Ronz Rocketz and @kuririn in Hawaii (or I should just mail it to you!)

We promise not to lose it. Oh wait, we already did before. Never mind…

 

[lakeroadster]

I pulled the 1st fin from the form today. I was a bit surprised at the amount of spring back, but the fin is still damp. I sanded the edges so they are now flat and uniform and then re-clamped the part without the wax paper.

When I made the ring fin for Ahpla it took it 4 or 5 days to fully dry. No worries.

 

[jmasterj]

Could you try forming the balsa alone first, allowing it to dry, and then adding the paper? That would allow different lengths of paper on the convex and concave fin faces. Feels like it would be stronger and more likely to hold form.

 

[lakeroadster]

Could you try forming the balsa alone first, allowing it to dry, and then adding the paper? That would allow different lengths of paper on the convex and concave fin faces. Feels like it would be stronger and more likely to hold form.

I'd still have to put the papered balsa back into the form... I'm not sure the added step would be on any benefit.

As to the size of the paper, when I make plywood, or papered fins, I always make the materials larger than needed, then after the plywood is dry, cut it just a bit oversized, then sand it to the finished size. For fins, I've learned to clamp them together during the sanding process and sand them all at once. This helps to ensure they are all the same size.

Hang tight. We'll let this dry a few more days, and then check it out.

 

[jmasterj]

Not trying to conserve paper. You're stretching the fibers in the paper on the outside and compressing them on the inside. If you apply the paper after forming, those fibers will be in a more neutral state. This intuitively seems good to me, but I don't really know whether it improves anything or not.

 

[BABAR]

I'd still have to put the papered balsa back into the form... I'm not sure the added step would be on any benefit.

As to the size of the paper, when I make plywood, or papered fins, I always make the materials larger than needed, then after the plywood is dry, cut it just a bit oversized, then sand it to the finished size. For fins, I've learned to clamp them together during the sanding process and sand them all at once. This helps to ensure they are all the same size.

Hang tight. We'll let this dry a few more days, and then check it out.

Suggestion. You may already have figured out how you are going to attach these to the body tube, with your engineering background. If not, you may want to consider “cheaters” or what I have also called “balsa fillets.”

cut a strip of balsa the same length as the fin root edge, the same thickness, and roughly the same width. Ideally it would be a cross grain cut, grain perpendicular to long edge, but those are hard to cut, easily breakable when handling, although much stronger when glued on. Long axis grain cuts will still work and are easier to cut and handle.

mark your body tube attachment sites, scuff it up with sandpaper and remark it again.

attach the balsa fillet so one edge matches your fin line, clockwise or counterclockwise edges doesn’t matter as long as you use same side for all your “cheaters.” If you like, you can bevel the cheater edge that will be OPPOSITE the alignment line before attachment. I like the double glue technique which you probably already use, and these are so light they tack easily and don‘t move. Make SURE the flat edge is perfectly aligned with your fin line.

once dry, you can attach the edges of your curved fins to the un-beveled side of each cheater.

benefits:

makes alignment really easy. As long as your lines are straight, and the cheater edge is straight, and your fin edge is straight, should line up perfectly.

provides a faster tack for the fins, (again I like double glue technique, although @kuririn ’s dab of CA a tech end is likely as good or better/faster), as you have more surface area to bond.

provides a much stronger bond, again because you have more surface area for attachment.

 

[lakeroadster]

Not trying to conserve paper. You're stretching the fibers in the paper on the outside and compressing them on the inside. If you apply the paper after forming, those fibers will be in a more neutral state. This intuitively seems good to me, but I don't really know whether it improves anything or not.

It's paper.

Did you notice in the previous photo how it curled up when the glue was applied? In this case, the papers' ability to resist the curling is negligible. It curls in this manner due to the papers grain direction.

 

[neil_w]

The method seems fine to me. The only possible alternative to consider is that rather than sandwiching between the two pieces of PVC (although that is very effective), if you just clamp the piece on the outside of a single form, then it'll be able to breath and dry faster, up to and including drying completely while still on the form.

The challenge is clamping it effectively, and sufficiently gently that you don't deform the edges of the wood. It's possible but can be a little tricky.

 

[lakeroadster]

The method seems fine to me. The only possible alternative to consider is that rather than sandwiching between the two pieces of PVC (although that is very effective), if you just clamp the piece on the outside of a single form, then it'll be able to breath and dry faster, up to and including drying completely while still on the form.

The challenge is clamping it effectively, and sufficiently gently that you don't deform the edges of the wood. It's possible but can be a little tricky.

You mention "it's possible", did you do this on one of your ring fin designs?

 

[neil_w]

You mention "it's possible", did you do this on one of your ring fin designs?

Yes:

• https://www.rocketryforum.com/threads/starship-avalon-build-thread.136389/post-1633859
• https://www.rocketryforum.com/threads/alcubierre-build-thread.148195/post-1818004

As mentioned, the clamping can be tricky, and I can imagine there are some circumstances where it's not practical. But I do like the ability to let the piece dry all the way while still on the form.

 

[lakeroadster]

Yes:

• https://www.rocketryforum.com/threads/starship-avalon-build-thread.136389/post-1633859
• https://www.rocketryforum.com/threads/alcubierre-build-thread.148195/post-1818004

As mentioned, the clamping can be tricky, and I can imagine there are some circumstances where it's not practical. But I do like the ability to let the piece dry all the way while still on the form.

However, when I checked the shape against the form, it turned out that they had released just a tiny bit of their curve:
View attachment 362582

Thanks @neil_w .​

​

Maybe the spring back is just a typical thing? I checked my curved fin again a few minutes ago, it seems dry and its i.d. conforms to the o.d. of the pipe, which is 3-1/2".​

​

I clamped it back up and will give it another 24 hours.​

Suggestion. You may already have figured out how you are going to attach these to the body tube, with your engineering background.

Thanks for the Cheat Sheet on Cheaters.​

​

I'm wanting to try the concept that @AeroTech posted a while back.. (see photo below). But in reality, I'm not sure what techniques I'll use. I just made this fin as a test mule to test the curved fin fixture. It's a fin without a rocket at this point.​

​

​

 

[neil_w]

Maybe the spring back is just a typical thing?​

I think it depends on the circumstance. Wood that is bent hard against the grain seems to want to spring back a bit. My Starship Avalon fins, by contrast, sprung back very little if at all (those were not bent as sharply *against the grain*.

A more concentrated dose of ammonia might help reduce springback as well.

 

[Dotini]

I'm very excited by these posts on forming balsa. This may very well turn out to be the best approach to HSR rocketry. But we will have to see. I'm sincerely appreciative of the contributions that are currently being made to the thread.

For my own part, I'm very interested in replicating the Figure 13 model. It looks as though these fins might have what is generally described as a 135 degree bend in the fins. What might be the easiest way to form balsa at this particular angle? What chance would a papered or otherwise reinforced butt joint have of surviving routine HSR landings?

Figure 13

 

[lakeroadster]

I'm very excited by these posts on forming balsa. This may very well turn out to be the best approach to HSR rocketry. But we will have to see. I'm sincerely appreciative of the contributions that are currently being made to the thread.

For my own part, I'm very interested in replicating the Figure 13 model. It looks as though these fins might have what is generally described as a 135 degree bend in the fins. What might be the easiest way to form balsa at this particular angle? What chance would a papered or otherwise reinforced butt joint have of surviving routine HSR landings?

Figure 13

I'd use homemade plywood made from 2 or 3 pieces of 1/32" Basswood, and do exactly what your suggested and use a butt joint and then paper them.

I've used homemade basswood ply on my Ahpla & THUNK! rockets, it's super strong.

 

[BABAR]

It's a fin without a rocket at this point.

​

​

well, we’ve already seen people make rockets that fly without fins, although making fins that fly without a rocket WOULD definitely be something new!

 

[lakeroadster]

It's a fin without a rocket at this point.

well, we’ve already seen people make rockets that fly without fins, although making fins that fly without a rocket WOULD definitely be something new!

What, you've never had a fin come off a rocket while the rocket was flying? I guess that would be a fluttering fin... maybe not a flying fin.

But wait, don't all the people that fly, who are from Finland, qualify as "Flying Fins"?